The present invention generally relates to industrial material handling. More particularly, the present invention relates to a unique handling assembly for fluid processing of an array of contact lenses. Typical fluid processing steps in the manufacture of soft contact lenses include hydration of the dry lens to a wet (soft) lens, and extraction of unwanted constituents remaining in the lens. The contact lenses are preferably supported upon a pallet which, together with a cooperatively configured cover, enables fluid processing of a plurality of contacts lenses in an efficient manner. The invention is also applicable to other types of ophthalmic lenses requiring fluid processing, for example, spectacle and intraocular lenses.
Static cast molding of contact lenses is known. See, for example, U.S. Pat. No. 5,466,147 issued to Bausch and Lomb Incorporated, the entire reference of which is incorporated herein by reference. A single mold unit comprises a female mold section having a concave optical surface and a male mold section having a convex optical surface. The female and male mold sections are complimentary shaped and mateable to form a lens-molding cavity between the facing concave and convex optical surfaces of the female and male mold sections, respectively.
The basic process for cast molding a lens is as follows. A quantity of liquid lens material (monomer) is dispensed into the concave optical surface of the female mold section and the male mold section is seated upon the female mold section with the concave and convex surfaces thereof facing one another to form a lens-shaped mold cavity. The joined female and male mold sections form a single mold unit which is subject to a curing cycle (e.g., by thermal or UV radiation) thereby causing polymerization of the lens material in the mold cavity. Once the lens material has cured, the male and female mold sections must be separated to retrieve the cured lens.
The opening or release of the mold sections must be carried out in a manner which will not harm the delicate lens. Once the lens has polymerized in the mold cavity, the lens and any lens flash will have an adhesive bond to the opposite concave and convex mold surfaces. Thus, the release of the male mold section from the female mold section must be of a force strong enough to break the adhesive bond of the lens and lens flash to the opposing mold surfaces, yet not so strong or haphazard that the optical surfaces of the lens are harmed by the release process. Should the lens crack or be otherwise damaged during the mold release process, the lens must be scrapped, thereby lowering the output yield and increasing manufacturing costs.
Once the mold sections have been separated, the lens must be released from the mold section on which it is retained. Both wet and dry release methods of lens release have been proposed in the prior art. In wet lens release methods, an aqueous solution is used to wet the hydrophilic lens which absorbs water and swells, causing the lens to separate from the mold surface. Once the lens has hydrated and released from its associated mold surface, the lens becomes a free-floating body in the hydrating fluid. If this process is carried out in a bath, there must thus be some means to contain the hydrated lens, yet not inhibit the access of the hydrating fluid to the interior of the mold and lens. Otherwise, the lenses must be xe2x80x9cfished outxe2x80x9d from the hydration bath using tweezers, a very labor intensive prospect.
Typically, the molds in which the lenses have been cured are carried on a support pallet in a predetermined array. Once the molds have been opened, the mold sections carrying the adhered lenses are transferred to a lens release station as discussed above. Once the lens has been released from the mold in which it is carried, the pallet of molds and lenses are readied for hydration/extraction processing.
It is desirable to be able to batch process contact lenses through different stations of a manufacturing process for efficiencies of manufacturing. It is thus desirable to be able to fluid process contact lenses in batches. Various methods of batch processing contact lenses through a fluid processing step have been proposed. The handling of the lenses during fluid processing include processes where the lenses are still in the mold or, alternatively, the lenses have been transferred to a different receptacle. It is furthermore known to use a bath process where batches of lenses may be submerged in a bath of fluid. It is also known to use sequential baths to ensure adequate fluid processing of the lenses. Alternatively, fluid may be applied to each individual contact in metered amounts, followed by extraction of the fluid from the mold section without disturbing the lens. This may be accomplished with the apparatus and method of U.S. Pat. No. 6,068,798 issued May 30, 2000 and which is assigned to the present assignee herein, Bausch and Lomb Incorporated.
An example of bath hydration may be seen in co-pending UK application no. 00079301 filed on Mar. 31, 2000 and which is assigned to the present assignee herein. In this method, a pallet containing an array of female mold sections having respective lenses adhered thereto is stacked on a pallet having a like array of empty male mold sections thereon. An empty pallet is stacked upon the female pallet to prevent the female mold sections from falling from the female pallet during hydration. The stack of three pallets form a single unit for bath hydration, although multiple units may be stacked together and placed in a carrier for submerging in the bath. The pallets are cooperatively configured such that the female and male mold sections are spaced by an amount sufficient to allow fluid to enter between the facing sections to reach the lens, but spaced small enough so as to prohibit the hydrated, loose lens from escaping from between the respective female and male mold sections. This method is especially geared toward a manufacturing method where the male mold section is used for packaging of the contact lens as seen in U.S. Pat. No. 5,573,108, also of common ownership with the instant application for patent.
In the case where the lenses must be transfer r ed from the mold in which they were formed to a separate package for downstream processes (e.g., hydration) or for final packaging to the consumer (e.g., transfer to a blister package), the lenses must undergo some amount of handling to effectuate this transfer process. In prior art methods, lenses have been transferred manually by an operator using a pair of tweezers to grasp the lens and transfer it from the mold to a package receptacle. This, of course, is an extremely labor intensive method of lens handling and also creates a high chance of lens damage caused by the direct contact with the tweezers and the operator""s inability to consistently control the amount of force used with the tweezers when handling a lens. The use of pick-and place units is also known for transferring lenses between stations, however, this must also be carried out with extreme precision so as to not damage or dislocate the lens during transfer.
Another example of lens hydration carriers may be seen in U.S. Pat. No. 5,476,111 to Anderson et al (Johnson and Johnson Vision Products, Inc. The ""111 patent discloses a lens transfer plate which first picks an array of female mold sections together with their associated lenses to form a first hydration carrier. The first hydration carrier is submerged in a bath to hydrate the lens through fluid passages extending through each lens pick-up. The mold section is then released, with the lens remaining with the lens transfer plate through surface tension. The lens transfer plate and lens assembly then couple to a hydrating base which has a like array of hydrating receptacles each having their own fluid passages for passing hydrating/extraction fluid to the lens contained therein. Once so treated, the lenses must be picked from the hydration base and transferred to yet another receptacle for further downline processing such as inspection and packaging, for example. The ""111 method and apparatus is rather complex in that it requires many complex robotic handling stations, as well as many handling components and carriers. Final packaging of the lenses is not discussed in any detail, although it is clear that the lenses must be removed from the handling carriers for transfer to a final package.
It is thus clear that lens handling is a critical parameter in the contact lens manufacturing line. Since contact lenses are extremely delicate, small articles of manufacture having precise optical surfaces, they must be handled with extreme care so as to not damage the lens and increase costs to the manufacturing operation. It is thus an object of a contact lens manufacturing line to use a contact lens handling system which minimizes the amount of direct contact of the handling apparatus with the lenses.
The present invention addresses the need for an efficient method of batch-processing contact lenses through various fluid processes. The invention provides a support for an array of dry contact lenses which may be individually carried in the mold in which they were formed, or in a different receptacle in which they have been previously deposited following removal from the mold. The invention further provides a unitary cover plate for positioning over the array of contact lenses on the support, thereby creating a fluid processing carrier unit. Multiple units may be stacked upon each other for batch processing.
The upper and lower surfaces of the cover plate are uniquely configured with a pattern of connecting grooves which create a series of fluid conduits. Thus, upon submerging the unit comprising the support, lenses and cover in a bath, fluid enters through the fluid conduits to reach and process the lenses. A second series of grooves form passages for the escape of air between the support, lenses and cover plate as they are placed in the bath, and also allow for the drainage of fluid as the support and cover plate are removed from the bath.
In a second aspect of the invention, the cover plate may optionally be also utilized as a stripper plate during transfer of lenses from their respective molds to receptacles positioned upon the support, as further discussed in co-pending U.S. patent application Ser. No. 09/540,250 filed on Mar. 31, 2000 and of common ownership herewith. When used in this manner, the cover provides an apparatus and method for transferring a dry contact lens from its associated mold section to a separate receptacle which is not only non-destructive to the lens, but also prevents the problem of unintentional lens displacement upon lens transfer to the receptacle.